week 22 chemistry

Percent Composition, Empirical Formulas, Molecular Formulas

Week 22 Chemistry

Warm Up: 3 Minutes

A certain bag of M&M’s has 8 blue candies, 7 red candies, 4 green candies, and 6 yellow candies. What percentage of the bag is blue M&M’s?

Record your Learning Target

You should be working SILENTLY

Stay in your own seat

Do the warm up in OneNote

Agenda

Warm Up [6 minutes] Pre-Lab/Expectations [7 minutes] Bubble Gum Lab [18 minutes] Answer Key [ 4 minutes] Modeling Tracking [5 minutes] You Track [10 minutes] Closing [3 Minutes]

Bubble Gum Lab

Problem

What percentage of Double Bubble Gum is composed of sugar?

Pre-Lab QuestionAccording to the nutritional manufacturer, each piece of gum has a mass of 6g with 5g of sugar. Using this information, what percent of the gum is sugar by mass?

%𝑆𝑢𝑔𝑎𝑟=𝑀𝑎𝑠𝑠𝑜𝑓 𝑆𝑢𝑔𝑎𝑟𝑀𝑎𝑠𝑠𝑜𝑓 𝐺𝑢𝑚

𝑥100 %

Lab Expectations

Work in assigned groups Raise your hand if you have a question No gum should be left on the desks

General information: How to do the lab1. Find the mass of your piece of gum before

chewing (include the wrapper)

2. Chew your gum for ~5 minutes

3. Find the mass of your piece of gum after chewing

Gum should be placed in wrapper before putting it on mass balance

4. Complete analysis and post-lab questions

Bubble Gum Lab

You each need One Piece of Gum and your Brain

Good Luck!!!

15 Minutes

Answer KeyAs Mr. Ghosh goes through the answers, highlight the ones you got wrong1. A

2. C

3. A

4. D

5. D

6. C

7. A

8. D

9. C

10. B

11. B

12. B

13. B

14. A

15. C

16. A

17. C

18. A

19. A

20. B

21. C

Class Averages (and Top Scores)

Period Top Score Class Average

1 95% 60%

3 100% 70%

4 90% 79%

5 90% 71%

6 100% 66%

7 95% 64%

What does Tracking Look Like?

Objectives

Questions on the

Exam

Your Points

Total Points

Percent Mastery

Bar Graph

Mastery85%  or

Chem.7C Lewis Dot Structure

s

What does Tracking Look Like?

Objectives

Questions on the

Exam

Your Points

Total Points

Percent Mastery

Bar Graph

Mastery85%  or

Chem.7C Lewis Dot Structure

s

1-5

What does Tracking Look Like?

Objectives

Questions on the

Exam

Your Points

Total Points

Percent Mastery

Bar Graph

Mastery85%  or

Chem.7C Lewis Dot Structure

s

1-5 ???

[3 if you got 3

out of 5 correct]

What does Tracking Look Like?

Objectives

Questions on the

Exam

Your Points

Total Points

Percent Mastery

Bar Graph

Mastery85%  or

Chem.7C Lewis Dot Structure

s

1-5 ???

[3 if you got 3

out of 5 correct]

5

What does Tracking Look Like?

Objectives

Questions on the

Exam

Your Points

Total Points

Percent Mastery

Bar Graph

Mastery85%  or

Chem.7C Lewis Dot Structure

s

1-5 ???

[3 if you got 3

out of 5 correct]

5 Your points x100 Total points

Percent MasteryCathy received 1 point out

of 4

possible points. What is

her percent mastery?

Your points x100 Total points

25%

What does Tracking Look Like?

Objectives

Questions on the

Exam

Your Points

Total Points

Percent Mastery

Bar Graph

Mastery85%  or

Chem.7C Lewis Dot Structure

s

1-5 ???

[3 if you got 3

out of 5 correct]

5 Your points x100 Total points

Shade in your % mastery

Your Turn

1. Go to shschem.weebly.com (our class website)

2. Hover over my page:Mr. Ghosh Homework Assignments ESL (or regular)

Chemistry

3. Under Homework Assignments, there is a new one labeled “Unit 5 Tracking”

4. Download (and save) this and fill it out

Closing

Explain the purpose of today’s lab

Warm Up: 4 Minutes

You should be working SILENTLY

Stay in your own seat

1.Log into your computer2.Go to m.socrative.com3.Enter room number: 2305384.Finish all questions

When you are finished, check your grades on PS Connect

Agenda

Warm Up [7 minutes] Notes/Examples [15 minutes] Guided Practice [12 minutes] Independent Practice [15 minutes] Closing [3 Minutes]

What is % Composition??

Percent by mass of eachelement in a compound

What is % Composition??

% compositionby mass=Massof partMass of Whole

x100 %

Example 1:

A compound contains 2.0g of sodium, 3.5g of oxygen, and 0.5 g of hydrogen. What is the percent composition of this compound?

Example 2:

What is the percent composition by mass of the elements in the compound, AgNO3?

Guided Practice

Teacher:

1. Will show the problem on the board Students:

1. Take 24 seconds to identify your given and unknown.

2. Take 46 seconds to speak with your shoulder partner about the problem

3. Be ready to share when Mr. Ghosh says SWAG

Guided Practice 1:

9.03 g Magnesium combines completely with 3.48 g Nitrogen to form a compound. What is the percent composition of Nitrogen in this compound?

27.82 % N

Guided Practice 2:

What is the percent composition by mass of the elements in Mercury (II) Oxide?

92.6% Hg7.4% O

Guided Practice 3:

What is the percent composition by mass of the elements in K2CO3?

56.6% K8.7% C

34.7% O

Independent Practice

Take some time to practice finding the %

composition of the following compounds

Practice makes Perfect

85%

Closing

How do you find the percent composition of an element in a compound?

Warm Up: 4 MinutesWrite the Learning

Target

You should be working SILENTLY

Stay in your own seat

1.Log into your computer2.Go to m.socrative.com3.Enter room number: 2305384.Finish all questions

When you are finished, check your grades on PS Connect

Agenda

Warm Up [7 minutes] Notes/Examples [15 minutes] Guided Practice [12 minutes] Independent Practice [15 minutes] Closing [3 Minutes]

Goal For Today

Percent Composition:

79.8% C, 20.2% H

Student Given: Student Answer:

CH3

Empirical Formulas

empirical formula of glucose = CH2O

Shows the lowest number ratio of atoms in a compound

Example 1:

What is the empirical formula for a chemical compound that is 79.8% C and 20.2% H?

Step 1: Convert Percent to Grams

Step 2: Convert Grams to Moles by dividing grams by the atomic mass of each element.

79.8% C and 20.2% H

How to Compose the Empirical Formula?

Step 3:Divide both molar quantities by the smallest mole quantity to determine the subscript for each element in the formula

79.8% C and 20.2% H

How to Compose the Empirical Formula?

Example 2:

What is the empirical formula for a compound that is 81.7% Be and 18.3% H?

Guided Practice

Teacher:

1. Will show the problem on the board Students:

1. Take 22 seconds to identify the elements involved.

2. Take 68 seconds to solve the problem with your shoulder partner

3. Be ready to share when Mr. Ghosh says SWAG

Guided Practice 1:

What is the Empirical Formula of a

compound that is 67.6% Hg, 10.8% S, and

21.6 % O by mass?

HgSO4

Guided Practice 2:

What is the Empirical Formula of a

compound that is 88.2 % Oxygen and

11.8% Hydrogen by mass?

H2O

Guided Practice 3:

What is the empirical formula of a

compound that is made from 50%

Cesium and 50% Iodine by mass?

CsI

Independent Practice

Practice makes Perfect

85%

Closing

What is the empirical formula?

How do you compose the empirical formula?

Warm Up: 4 Minutes

You should be working SILENTLY

Stay in your own seat

1.Log into your computer2.Go to m.socrative.com3.Enter room number: 2305384.Finish all questions

When you are finished, check your grades on PS Connect

Agenda

Warm Up [7 minutes] Notes/Examples [15 minutes] Guided Practice [12 minutes] Independent Practice [15 minutes] Closing [3 Minutes]

More Empirical Formulas!!

Writing Empirical FormulasMost of the time, our mole ratios come out close to a whole number (~.9, ~.1):

Examples: 1.992 2

Ratio from Calculator

What we assume

16.00412

4.962

6.071 6

5

16

But what if our mole ratio comes out to something like 1.501? What do we do then?

Example 1:

What is the empirical formula for a chemical compound that is 49.1% Be and 50.9% N?

Common Decimals/Fractions

When we find a mole ratio that ends up close to a common decimal/fraction:

X.33X.66

X.75X.5X.25

We must multiply these ratio values by a specific number

Mole Ratio Multiply all mole ratios by

Table of Common Decimals/Fractions

Mole Ratio Multiply all mole ratios by

X.5

Table of Common Decimals/Fractions

Mole Ratio Multiply all mole ratios by

X.5 2

Table of Common Decimals/Fractions

Mole Ratio Multiply all mole ratios by

X.5 2X.33

Table of Common Decimals/Fractions

Mole Ratio Multiply all mole ratios by

X.5 2X.33 3

Table of Common Decimals/Fractions

Mole Ratio Multiply all mole ratios by

X.5 2X.33 3X.66

Table of Common Decimals/Fractions

Mole Ratio Multiply all mole ratios by

X.5 2X.33 3X.66 3

Table of Common Decimals/Fractions

Mole Ratio Multiply all mole ratios by

X.5 2X.33 3X.66 3X.75

Table of Common Decimals/Fractions

Mole Ratio Multiply all mole ratios by

X.5 2X.33 3X.66 3X.75 4

Table of Common Decimals/Fractions

Mole Ratio Multiply all mole ratios by

X.5 2X.33 3X.66 3X.75 4X.25

Table of Common Decimals/Fractions

Mole Ratio Multiply all mole ratios by

X.5 2X.33 3X.66 3X.75 4X.25 4

Table of Common Decimals/Fractions

Example 1:

What is the empirical formula for a chemical compound that is 49.1% Be and 50.9% N?

Example 2:

What is the empirical formula of a compound that is 25.9% Nitrogen and 74.1 % Oxygen by mass?

Guided Practice

Teacher:

1. Will show the problem on the board Students:

1. Take 22 seconds to identify the elements involved.

2. Take 68 seconds to solve the problem with your shoulder partner

3. Be ready to share when Mr. Ghosh says SWAG

Guided Practice 1:

What is the Empirical Formula of a

compound that is 25.9% P and 74.1% Cl?

P2Cl5

Guided Practice 2:

What is the Empirical Formula of a compound that is 17.4% Nitrogen and 82.6% Fluorine?

N2F7

Guided Practice 3:

What is the Empirical Formula of a compound that is made from 35.9% Aluminum and 64.1% Sulfur?

Al2S3

Independent Practice

Practice makes Perfect

85%

Closing

What is the empirical formula?

How do you compose the empirical formula?

Warm Up: 4 MinutesWrite the Learning

Target

You should be working SILENTLY

Stay in your own seat

1.Log into your computer2.Go to m.socrative.com3.Enter room number: 2305384.Finish all questions

When you are finished, check your grades on PS Connect

Agenda

Warm Up [6 minutes] Notes/Examples [11 minutes] Guided Practice [9 minutes] Quiz [20 minutes] Closing [1 Minute]

Goal For Today

Empirical Formula:

CH4O

Molar Mass of Molecular

Formula: 96 g/mol

Student Given: Student Answer:

Molecular Formula:

C3H12O3

Molecular Formulas

Molecular formula of glucose = C6H12O6

Shows exactly how many of each atom is in a compound

(unsimplified formula)

Check Point #1

Is CH2 an empirical or a molecular formula?

Empirical

Check Point #2

Is S3O6 an empirical or a molecular formula?

Molecular(Empirical Formula is SO2)

Example 1:

What is the molecular formula if the empirical formula is CH4O and the mass of the whole molecule is 96 g/mol?

Step 1: Find the Mass of the Empirical Formula

Step 2: Divide the mass of the Molecular Formula by the mass of the Empirical Formula

Empirical Formula: CH4O

Mass of Molecular Formula: 96

g/mol

How to Compose the Molecular Formula?

Step 3: Multiply the

subscripts in the

empirical formula by the

answer from step 2.

Empirical Formula: CH4O

Mass of Molecular Formula: 96

g/mol

How to Compose the Molecular Formula?

Example 2:

Compose the molecular formula of the compound whose molar mass is 60.0 g/mol and empirical formula is CH4N.

Guided Practice

Teacher:

1. Will show the problem on the board Students:

1. Take 22 seconds to identify the elements involved.

2. Take 68 seconds to solve the problem with your shoulder partner

3. Be ready to share when Mr. Ghosh says SWAG

Guided Practice 1:

Compose the molecular formula of the compound whose molar mass is 90 g/mol and empirical formula is CH2O.

C3H6O3

Guided Practice 2:

Compose the molecular formula of the compound whose molar mass is 62 g/mol and empirical formula is CH3O.

C2H6O2

Independent Practice

Practice makes Perfect

85%

Material Covered on Quiz

Mole Calculations (1 and 2 step)Percent CompositionEmpirical Formulas

Goal

To demonstrate mastery, we are shooting for

85%

Check Point

What is your goal for this quiz?

85%

Expectations for Quiz

Clear your desk of everything except a....

1. Writing Utensil

2. Calculator

Periodic Table is provided to you

Expectations

Students will keep eyes on own paper

Cheating will result in an automatic ZERO Students will remain SILENT for the duration of the

quiz

Good Luck!!

Closing

How was your quiz?

What topics do you feel you still need review on?